1. Field of the Invention
This invention relates to the production of hydrogen. In one aspect, the invention relates to the production of hydrogen from the reaction of hydrogen sulfide and carbon monoxide while in another aspect, the invention relates to the use of heteropolyanionic metal complex catalysts to promote this reaction.
2. Description of the Prior Art
Hydrogen is a valuable resource as both a fuel source and chemical feedstock and as such, its production has received much attention from the chemical industry. Presently, the dominant industrial method of production is the reaction of steam with natural gas (steam reforming) although various other methods are known. Of these other methods, one that is of particular interest is the oxidation of hydrogen sulfide with carbon monoxide to produce hydrogen and carbonyl sulfide.
This reaction is of particular interest for several reasons, one of which is that hydrogen sulfide is a relatively inexpensive material and is available in large quantities from the desulfurization of fossil fuels and sour natural gas deposits. Presently this material is considered more of a waste problem than a feedstock and is typically oxidized by the Claus process to water and elemental sulfur.
Another reason for the interest in this reaction is that it can be combined with other reactions to form various thermochemical cycles, such as
______________________________________ H.sub.2 S + CO.fwdarw.H.sub.2 + COS (a) COS + O.sub.2 .fwdarw.CO + SO.sub.2 (b) H.sub.2 S + O.sub.2 .fwdarw.H.sub.2 + SO.sub.2 (c) ______________________________________
The second step which enables the recycle of relatively expensive carbon monoxide makes this thermochemical cycle economically attractive. In effect, hydrogen sulfide is converted to hydrogen and sulfur dioxide, the latter being a useful resource in the manufacture of sulfuric acid.
While the reaction of hydrogen sulfide and carbon monoxide to produce hydrogen and carbonyl sulfide is known, few catalysts have been identified as useful for promoting it. Fukuda et al. describe in several publications the use of various metal sulfides, e.g. titanium disulfide, zinc sulfide, copper sulfide, nickel sulfide, etc. See U.S. Pat. No. 3,856,925; Journal of Catalysis, 49, 379 (1977); and Bulletin of Chemistry for Japan, 51, 150 (1978). However, since these disclosures describe relatively few catalysts, there is a continuing interest in identifying new catalysts for this reaction.